# coding: utf-8
import math

x1,y1,x2,y2 = map(float,input().split())
d = math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2)

print("{:.6f}".format(d)) import math math x1,y1,x2,y2 = map(float,input().split()) x1 map(float,input().split()) map float input().split() ().split () input split y1 x2 y2 d = math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2) d math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2) math.sqrt math sqrt (x2 - x1) ** 2 + (y2 - y1) ** 2 (x2 - x1) ** 2 x2 - x1 x2 x1 2 (y2 - y1) ** 2 y2 - y1 y2 y1 2 print("{:.6f}".format(d)) print "{:.6f}".format(d) "{:.6f}".format "{:.6f}" format d y1,x2,y2 = map(float,input().split()) map(float,input().split()) y1 x1,y1,x2,y2 = map(float,input().split()) map(float,input().split()) x1 x2,y2 = map(float,input().split()) map(float,input().split()) x2 d = math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2) math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2) d y2 = map(float,input().split()) map(float,input().split()) y2
# coding: utf-8
import math

x1,y1,x2,y2 = map(float,input().split())
d = math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2)

print("{:.6f}".format(d))